Details of Masood's lengthy criminal history have continued to emerge since Wednesday's terrorist attack.

The 52-year-old hit pedestrians on Westminster Bridge with a car before crashing into railings outside Parliament and fatally stabbing PC Keith Palmer in the grounds of the Palace of Westminster. Three other innocent victims were killed.

Masood was shot dead by armed police moments later.

Fears are also growing he may have been groomed for extremism during his time in prison, with a childhood friend claiming the killer turned to Islam and changed his name to Khalid Masood after serving a jail term for assaulting someone with a knife.

The victim, Piers Mott, was left with a three-inch gash on his cheek and needed 20 stitches after the pub car park attack in East Sussex.

Masood's sudden religious conversion will add to concerns that criminals are being brought under the influence of hardened jihadists behind bars, something which the Government admitted was a "growing problem" last year.

Scotland Yard says a 27-year-old man and a 58-year-old man who were arrested following raids in Birmingham on Thursday remain in police custody, as detectives try to determine whether Masood acted alone or was "encouraged, supported or directed" by others.

Yesterday, Sky News learned Masood had used the WhatsApp phone messaging service two minutes before he attacked, but it is unclear whether he was communicating with someone.

Detectives have seized 2,700 items, including "massive amounts" of computer data, following raids nationwide - and approximately 3,500 witnesses have talked to police.

Police have confirmed extra officers are being deployed for England's World Cup qualifier against Lithuania tomorrow.

Armed patrols will take place around Wembley Stadium, and a minute's silence will be held before kick-off at 5pm.